Andrew Liszewski

To no one's surprise, those clear plastic protractors we were all taught to use in grade school are far from being the most accurate way to measure an angle. They're perfect for a grade five homework assignment, but in the real world you'll probably want to opt for this digital alternative that's precise to plus or minus 0.3 degrees.

For $20 it's cheap enough for professionals, students, and anyone who likes to putz around with random contraptions on their desk—and on a single cell-sized battery you can expect to get about 3,000 hours of use out of it. For anyone not intending to use it as a toy, a locking mechanism keep the rulers at the angle of your choice when drawing lines, while a set of holes at either end let you hang or anchor it in place for tricky measurements. It almost makes me want to go back to school again. (Not in a thousand years.)